我正在创建一个带有 flutter 的绘图 Canvas ,我想同时使用缩放(用于缩放、平移和旋转)和平移(用于用手指绘图)手势,但 flutter 不允许这样做,因为缩放是平移的超集。有什么解决方法吗?
我尝试创建自己的自定义手势识别器来检测屏幕上的指针数量,以便如果两个指针在短时间内(比如说 1 秒)与屏幕接触,则 Scale 接管,否则 pan 开始使用第一个触摸屏幕的指针。我正在使用 matrix_gesture_detector用于缩放部分的包。
这是我的自定义手势识别器代码
class ScaleAndPanRecognizer extends OneSequenceGestureRecognizer {
var manager = GestureArenaManager();
final Function onPanDown;
final Function onPanUpdate;
final Function onPanEnd;
ScaleAndPanRecognizer({
@required this.onPanDown,
@required this.onPanUpdate,
@required this.onPanEnd,
});
int numPointers = 0;
int timeFrame = 1;
int pointer1;
int pointer2;
var time1;
var time2;
var position1;
@override
void addPointer(PointerDownEvent event) {
print(numPointers);
if (numPointers == 0) {
pointer1 = event.pointer;
print(pointer1);
position1 = event.localPosition;
manager.hold(pointer1); //hold the assignment for this pointer for now
startTrackingPointer(pointer1);
numPointers += 1;
time1 = DateTime.now();
} else if (numPointers == 1) {
pointer2 = event.pointer;
print(pointer2);
resolvePointer(pointer2, GestureDisposition.rejected);
time2 = DateTime.now();
var diff = time2.difference(time1);
print(diff);
if (diff <= Duration(seconds: timeFrame)) {
manager.release(pointer1);
resolvePointer(pointer1, GestureDisposition.rejected);
} else {
resolvePointer(pointer1, GestureDisposition.accepted);
manager.release(pointer1);
onPanDown(position1);
}
numPointers = 0;
}
}
@override
void handleEvent(PointerEvent event) {
if (event is PointerMoveEvent) {
onPanUpdate(event.localPosition);
}
if (event is PointerUpEvent) {
onPanEnd();
stopTrackingPointer(event.pointer);
}
}
@override
String get debugDescription => 'only one pointer recognizer';
@override
void didStopTrackingLastPointer(int pointer) {}
}
最佳答案
你要做的是替换onPanUpdate, onPanEnd...
与 onScaleUpdate, onScaleEnd...
.然后只是代替details.globalPosition
使用 details.focalPoint
.您将获得与 Pan 相同的行为,而且您现在可以访问 details.scale
或 details.rotation
.这是一个例子。
前:
onPanUpdate: (DragUpdateDetails details){
newPosition = details.globalPosition;
//scale and rotation missing in pan
},
后:onScaleUpdate: (ScaleUpdateDetails details){
newPosition = details.focalPoint;
newRotation = details.rotation;
newScale = details.scale;
//scale and rotation now available
},
希望这可以帮助。我也花了一些时间才弄清楚。
关于android - Flutter:同时使用 Pan 和 Scale 手势?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61489657/